Drugs, Alcohol Send Boston Concertgoers to Hospital

Dozens of teen concertgoers were hospitalized after an electronic dance music show at Boston's TD Garden arena Wednesday, many suffering from a combination of heat and alcohol.

Thirty-six people were taken to area hospitals and another 50 were treated at scene, officials told ABC News. Officials at Tufts Medical Center said at least nine patients were brought there, while Massachusetts General Hospital treated 13 patients, hospital officials said. All of the injuries are nonlife-threatening.

Signs of illicit drugs, including the popular club drug "Molly" - a form of ecstasy - were apparent, with concertgoers strapped to stretchers, some still screaming and flailing their arms.

"There was a girl all alone, she was passed out for some time," Chad Dyson, who attended the concert with friends, told ABC News. "She was limp. Shortly after that, she started vomiting. They had EMS come by and actually took her away in a chair, strapped her down and took her out of the venue."

Dyson said the girl was passed out before the concert headliner, Swedish disc jockey Avicii, performed.

"I counted five separate ambulances and almost, they even had like a mobile command center set up as well, looked like a mobile command fire truck," Dyson said.

Beyond the hospitalized concertgoers, dozens more were treated onsite, with police describing the situation as a mass casualty event because of the number of people involved.

The incident continues a concert trend of drug-related emergencies. Drugs and alcohol sent nearly 30 people to the hospital at another Avicii concert in Toronto last month.

Three concert deaths last year were allegedly tied to Molly overdoses, including two at the Electric Zoo Festival in New York City, and another at a ZED Concert at Boston's House of Blues.

Hours after the show, Avicii - whose real name is Tim Bergling - posted his condolences to the victims online.

"Its [sic] a terrible thing, I rly [sic] hope everyone is ok! My thoughts go to those affected & their families," he wrote on Twitter.

ABC News' Elara Mosquera and ABC News Radio contributed to this report.